5.5 - Plant Diseases

Plant diseases and their signs

• Plants can be infected by the same types of pathogen as animals: viruses, bacteria, and fungi.
• They can also be infested and damaged by larger organisms, such as insects.
• It's usually fairly clear when a plant has a disease, because diseased plants show characteristic signs.
• Different diseases produce different combinations of these signs - that's what makes it possible to tell one disease from another.

Ash dieback - A fungal disease

• Ash dieback is a disease of ash trees caused by a fungus.
• It's carried from tree to tree through the air by the wind.
• It produces leaf loss and lesions on the bark, and eventually kills the tree.

Common signs of plant disease

• Stunted growth
• Spots on the leaves
• Patches of decay or rot
• Abnormal growths, such as lumps
• Malformed stems or leaves
• Discolouration